acpi: enable C3 Power State on Dell Inspiron 8200

diff -puN drivers/acpi/processor_idle.c~acpi-enable-c3-power-state-on-dell-inspiron-8200 drivers/acpi/processor_idle.c
@@ -72,6 +72,8 @@ module_param(max_cstate, uint, 0644);
 static unsigned int nocst __read_mostly;
 module_param(nocst, uint, 0000);
 
+static int forced_c3;
+
 /*
  * bm_history -- bit-mask with a bit per jiffy of bus-master activity
  * 1000 HZ: 0xFFFFFFFF: 32 jiffies = 32ms

@@ -106,6 +108,20 @@ static int set_max_cstate(struct dmi_sys
 	return 0;
 }
 
+/*
+ * Some (Dell) machines have a too large C3 latency set, but it still works completely.
+ * Dell provides a driver for other operating systems to hack around this bug, so we know
+ * it's safe.
+ */
+static int dmi_force_c3(struct dmi_system_id *id)
+{
+	forced_c3 = 1;
+
+	printk(KERN_NOTICE PREFIX "%s detected - Force enabling C3.", id->ident);
+
+	return 0;
+}
+
 /* Actually this shouldn't be __cpuinitdata, would be better to fix the
    callers to only run once -AK */
 static struct dmi_system_id __cpuinitdata processor_power_dmi_table[] = {

@@ -164,6 +180,9 @@ static struct dmi_system_id __cpuinitdat
 	  DMI_MATCH(DMI_BIOS_VENDOR,"Phoenix Technologies LTD"),
 	  DMI_MATCH(DMI_BIOS_VERSION,"SHE845M0.86C.0013.D.0302131307")},
 	 (void *)2},
+	{ dmi_force_c3, "Dell Inspiron 8200", {
+	  DMI_MATCH(DMI_SYS_VENDOR,"Dell Computer Corporation"),
+	  DMI_MATCH(DMI_PRODUCT_NAME,"Inspiron 8200") }, NULL},
 	{},
 };
 

@@ -975,11 +994,12 @@ static void acpi_processor_power_verify_
 	 * C3 latency must be less than or equal to 1000
 	 * microseconds.
 	 */
-	else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
+	if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY && !forced_c3) {
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "latency too large [%d]\n", cx->latency));
 		return;
-	}
+	} else if (forced_c3)
+		cx->latency = ACPI_PROCESSOR_MAX_C3_LATENCY;
 
 	/*
 	 * PIIX4 Erratum #18: We don't support C3 when Type-F (fast)